Process for recovering ammonium adipate through combination of reverse osmosis and membrane distillation

Abstract

The invention discloses a process for recovering ammonium adipate through combination of reverse osmosis and membrane distillation. The process comprises the following steps of alkalization impurity removal, nanofiltration impurity removal, reverse osmosis recovery and nanofiltration concentrated liquid recovery. According to the method, high-purity recovery of the feed medium ammonium adipate can be realized, so that the problem that chlorine-containing waste ammonium adipate cannot be recycled to a production line is solved, resource waste is reduced, the production cost is reduced, and total nitrogen in sewage is reduced; the raw materials except the ammonia water are all from a production line, no new impurities are introduced in the recovery process, the recovery cost is low, the raw materials are easy to obtain, and large-scale popularization and application are easy.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a process for recovering ammonium adipate by combining reverse osmosis and membrane distillation. Background Art

[0002] Aluminum electrolytic electrode foil is an important raw material for the manufacture of aluminum electrolytic capacitors. During the production process, a large amount of feed dielectric (such as ammonium citrate, ammonium adipate, etc.) is required, and a large amount of water is used to clean the foil surface. This part of the bath liquid and cleaning liquid has high COD and ammonia nitrogen and cannot be discharged directly. The general bath liquid treatment method is to recycle it until the impurities in the bath liquid are enriched to the point where they affect product quality. It is then transferred to a biochemical system for treatment together with the cleaning water. Although this treatment method can maintain production intermittently, it has a significant impact on product quality and production costs, increasing the company's environmental protection treatment pressure, while also increasing the use of ammonium adipate, resulting in a waste of resources. Summary of the Invention

[0003] The present invention aims to address the aforementioned problems existing in the prior art by providing a process for recovering ammonium adipate using a combination of reverse osmosis and membrane distillation. This process addresses the problem of ammonium adipate being unable to be directly recycled back into the production line, offering advantages such as lower production costs, reduced total nitrogen content in wastewater, low energy consumption, and an environmentally friendly process.

[0004] The technical solution adopted in the present invention is as follows:

[0005] A process for recovering ammonium adipate by combining reverse osmosis and membrane distillation comprises the following steps:

[0006] S1. Alkalization and impurity removal

[0007] Add ammonia water to the ammonium adipate tank solution, stop adding when the pH value reaches 6-8, stir and mix for 0.5-1h, and then pump the mixture through the activated carbon box and the safety filter into the nanofiltration liquid supply tank;

[0008] S2, nanofiltration to remove impurities

[0009] Open the nanofiltration concentrate valve outlet and the nanofiltration liquid supply pump, and after the nanofiltration concentrate flow rate stabilizes, start the nanofiltration high-liquid pump, adjust the high-liquid pump frequency and the concentrate valve opening to control the nanofiltration operating pressure at 1.5-3.5 MPa, and collect the nanofiltration dilute liquid and nanofiltration concentrate;

[0010] S3, reverse osmosis recovery

[0011] Adding cleaning water 3-8 times the volume of the nanofiltration dilute liquid into the reverse osmosis liquid supply tank and circulating and stirring evenly, then opening the reverse osmosis concentrate valve outlet and the reverse osmosis industrial pump, starting the reverse osmosis high-pressure pump after the reverse osmosis flow stabilizes, adjusting the high-liquid pump frequency and the concentrate valve opening to control the nanofiltration operating pressure at 1.5-3.5 MPa, and returning the reverse osmosis concentrate to the reverse osmosis liquid supply tank; when the reverse osmosis concentrate has an electrical conductivity of ≥30,000 μs / cm and a chloride ion concentration of <1 ppm, recovering it as a liquid product, ammonium adipate aqueous solution;

[0012] S4, nanofiltration concentrate recovery

[0013] Open the membrane evaporation feed valve and membrane evaporation vacuum pump, and when the vacuum degree stabilizes to above -0.09MPa, open the membrane evaporation steam valve to carry out low-temperature concentration of the nanofiltration concentrate. When the specific gravity of the original liquid tank is detected to be 1.2-1.4, transfer it to the crystallization equipment, open the cooling water valve and slowly cool it to 5-15℃, keep it warm for 2-4h and centrifuge it. After the solid is washed with a small amount of 0-5℃ water, it is a qualified ammonium adipate solid product.

[0014] Preferably, the concentration of the ammonia water in S1 is 5%-25%.

[0015] Further preferably, the dilute liquid recovered by reverse osmosis in S3 is collected into a cooling water pool for replenishing water in the cooling pool of the production system.

[0016] More preferably, in S4, the material temperature is controlled at 50-80°C during the low-temperature concentration process.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention achieves a nanofiltration recovery volume recovery rate of more than 95% and an impurity metal ion removal rate of more than 95% by optimizing the nanofiltration membrane and pressure flow control; and achieves an ammonium adipate permeability of less than 5% and a chloride ion removal rate of more than 95% by optimizing the reverse osmosis membrane and pressure flow control. Therefore, the present invention can realize the recovery of the feed medium ammonium adipate, thereby solving the problem that chlorine-containing waste ammonium adipate cannot be reused in the production line, reducing resource waste, lowering production costs, and reducing total nitrogen in wastewater.

[0019] (3) The reverse osmosis recovered water is washed and impurities removed in the present invention and added to the ammonium adipate cleaning water of the production line, which not only solves the cleaning water treatment problem but also saves the water cost of the recovery process; the energy consumption per ton of water is reduced to below 0.35 by adjusting the membrane concentration temperature and the discharge density; the overall process has no other wastewater, solid and gas discharge except the filter material that is replaced regularly, and basically achieves zero emission recovery. Therefore, the process of the present invention has significant energy-saving and consumption-reducing advantages, and the raw materials used, except ammonia water, are all derived from the production line. No new impurities are introduced during the recovery process, the recovery cost is low, the raw materials are easy to obtain, and it is easy to promote and apply on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flow chart of the process of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] 1. Alkalization and impurity removal

[0024] Transfer 3m 3 Start stirring the ammonium adipate tank on the production line and slowly add 40kg of 25% aqueous ammonia in batches. Maintain stirring for 0.5h and check the pH to 7.32. Open the net outlet valves of the activated carbon box and the safety filter, open the bottom valve of the alkalization kettle, and start the transfer pump. After alkalization, the material passes through the activated carbon box and the safety filter and enters the nanofiltration liquid supply tank.

[0025] 2. Nanofiltration to remove impurities

[0026] Check and confirm that the material in the nanofiltration liquid supply tank is sufficient for one round of recycling and processing, open the inlet and outlet of the nanofiltration equipment and the valve of the concentrated and dilute liquid flowmeter, turn on the liquid supply pump, and turn on the nanofiltration high-pressure pump after the concentrated liquid flow is stable, adjust the high-pressure pump frequency and the concentrated liquid valve opening, and control the operating pressure at 1.5-3.5MPa. The nanofiltration dilute liquid is collected in the reverse osmosis liquid supply tank for reverse osmosis recovery (step 3); the nanofiltration concentrated liquid is collected in the concentrated liquid transfer tank for subsequent process treatment (step 4). This process is recycled under three pressure conditions of 1.5MPa, 2.5MPa, and 3.5MPa respectively, to obtain the intermediate process product nanofiltration concentrated liquid 1-3 after nanofiltration impurity removal, with a volume recovery rate between 75-95% and a metal ion removal rate of more than 80%. Some operating data are shown in Table 1:

[0027] Table 1

[0028] name Pressure / MPa Volume recovery rate / % <![CDATA[Cu 2+ / ppm]]> <![CDATA[Fe 2+ / ppm]]> Original solution / / 1.02 0.74 Nanofiltration concentrate 1 1.5 75 Not detected Not detected Nanofiltration concentrate 2 2.5 82 0.01 0.01 Nanofiltration concentrate 3 3.5 95 0.04 0.06

[0029] Table 1 shows that adjusting the nanofiltration operating pressure can effectively remove impurity metal ions in the material. In particular, when the nanofiltration pressure is operated at 3.5 MPa, the volume recovery rate of impurity removal is 95%, the metal ion removal rate is 94.3%, and the individual impurities are all below 0.1 ppm, which meets the requirements of enterprise use.

[0030] 3. Reverse osmosis recovery

[0031] Check and confirm that the material in the reverse osmosis liquid supply tank is sufficient for one round of recycling and processing, add 3-8 times the volume of nanofiltration dilute liquid (the nanofiltration dilute liquid obtained after running nanofiltration at 3.5MPa to remove impurities) to the reverse osmosis liquid supply tank, circulate and stir evenly with cleaning water, open the inlet and outlet of the reverse osmosis equipment and the concentrated and dilute liquid flow meter valves, start the liquid supply pump, and start the reverse osmosis high-pressure pump after the concentrated liquid flow stabilizes, adjust the high-pressure pump frequency and the concentrated liquid valve opening, control the operating pressure at 2.8MPa, and return the reverse osmosis concentrated liquid to the reverse osmosis liquid supply tank, and collect the dilute liquid into the cooling water pool for water replenishment of the production system cooling pool. During the reverse osmosis recovery operation, test the concentrated liquid conductivity and chloride ion concentration. When the conductivity is ≥30000μs / cm and the chloride ion concentration is <1ppm, the recovered product qualified concentrated liquid is transferred to the product tank for reuse in the production process. The qualified concentrated liquid is the aqueous solution of ammonium adipate. The main components of the ammonium adipate aqueous solution are ammonium adipate and water. Its composition is the same as that of a feed medium in the production process, so it can be directly reused in the production process without refining it into ammonium adipate solid. This process recovers ammonium adipate aqueous solution 1-3 and dilute solution 1-3 at dilution ratios of 3 times, 5 times, and 8 times water, respectively. The ammonium adipate recovery rate can reach 95%, and the chloride ion removal rate is above 95%. The operating data is shown in Table 2:

[0032] Table 2

[0033]

[0034] From the table above, it can be seen that chloride ions in the bath solution can be effectively removed by adjusting the water ratio. In particular, when the water volume is 3-5 times, the residual chloride ion content is less than 1ppm, which meets the enterprise's use standards. At the same time, the ammonium adipate recovery rate is above 93%. Under this condition, the economic benefit of operation and recovery is relatively high.

[0035] The conductivity of reverse osmosis dilute liquid is shown in Table 3:

[0036] Table 3

[0037] name Water ratio Dilute liquid conductivity μs / cm pH Light liquid 1 3 times 520 7.1 Light liquid 2 5 times 460 7.2 Light liquid 3 8 times 400 7.1

[0038] From the data in the table above, we can see that the pH of reverse osmosis dilute liquid is basically neutral, and the conductivity is less than 600μs / cm, which is close to the conductivity of tap water and can be directly used for water replenishment in production cooling pools.

[0039] 4. Nanofiltration concentrate recovery

[0040] Confirm that the material in the nanofiltration concentrate tank (the nanofiltration concentrate is obtained after nanofiltration and impurity removal at 3.5MPa in step 2) is sufficient for one round of recovery and treatment, open the membrane evaporation feed valve, membrane evaporation vacuum pump, and open the membrane evaporation steam valve after the vacuum degree stabilizes to above -0.09MPa to carry out low-temperature concentration of the nanofiltration concentrate. During the concentration process, the material temperature is controlled at 50-80℃. At the same time, the specific gravity of the original liquid tank is detected. When it is 1.25, it is transferred to the crystallization equipment, the cooling water valve is opened and slowly cooled to 10℃, kept warm for 3 hours, and centrifuged. After the solid is washed with a small amount of 0-5℃ water, it is a qualified ammonium adipate solid product. The ammonium adipate solid product can be mixed with the liquid product ammonium adipate aqueous solution in the reverse osmosis recovery process. The centrifugal mother liquor and the production line tank liquid are mixed and then enter the next round of treatment; the membrane evaporation produced water and the steam condensate are mixed and collected and used as raw materials for water production in the pure water workshop. The overall process has no external wastewater discharge. The specific input and output are shown in Table 4:

[0041] Table 4

[0042]

[0043] The test results of the obtained solid ammonium adipate product are shown in Table 5:

[0044] Table 5

[0045] name index purity 99.9％ Fe 0.1ppm Cu 0.1ppm Cl 0.9ppm

[0046] From the above table, it can be seen that the impurity content of the obtained solid ammonium adipate product meets the enterprise's usage standards and can be directly used for liquid preparation in the production line.

[0047] The description and drawings of the present invention are considered to be illustrative rather than restrictive. On the basis of the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features according to the disclosed technical content without creative work, and all of them are within the scope of protection of the present invention.

Claims

1. A process for recovering ammonium adipate by combining reverse osmosis and membrane distillation, characterized in that: The following steps are involved: S1. Alkalization and impurity removal Add ammonia water to the ammonium adipate tank solution, stop adding when the pH value reaches 6-8, stir and mix for 0.5-1h, and then pump the mixture through the activated carbon box and the safety filter into the nanofiltration liquid supply tank; S2, nanofiltration to remove impurities Open the nanofiltration concentrate valve outlet and the nanofiltration liquid supply pump, and after the nanofiltration concentrate flow rate stabilizes, start the nanofiltration high-liquid pump, adjust the high-liquid pump frequency and the concentrate valve opening to control the nanofiltration operating pressure at 1.5-3.5 MPa, and collect the nanofiltration dilute liquid and nanofiltration concentrate; S3, reverse osmosis recovery Adding cleaning water 3-8 times the volume of the nanofiltration dilute liquid into the reverse osmosis liquid supply tank and circulating and stirring evenly, then opening the reverse osmosis concentrate valve outlet and the reverse osmosis industrial pump, starting the reverse osmosis high-pressure pump after the reverse osmosis flow stabilizes, adjusting the high-liquid pump frequency and concentrate valve opening to control the nanofiltration operating pressure at 1.5-3.5 MPa, and returning the reverse osmosis concentrate to the reverse osmosis liquid supply tank; when the reverse osmosis concentrate has an electrical conductivity of ≥30,000 μs / cm and a chloride ion concentration of <1 ppm, recovering it as a liquid product, ammonium adipate aqueous solution; S4, nanofiltration concentrate recovery Open the membrane evaporation feed valve and membrane evaporation vacuum pump, and when the vacuum degree stabilizes to above -0.09MPa, open the membrane evaporation steam valve to carry out low-temperature concentration of the nanofiltration concentrate. When the specific gravity of the original liquid tank is detected to be 1.2-1.4, transfer it to the crystallization equipment, open the cooling water valve and slowly cool it to 5-15℃, keep it warm for 2-4h and centrifuge it. After the solid is washed with a small amount of 0-5℃ water, it is a qualified ammonium adipate solid product.

2. The process according to claim 1, characterized in that The concentration of the ammonia water in S1 is 5%-25%.

3. The process according to claim 1, characterized in that The dilute liquid recovered by reverse osmosis in S3 is collected in the cooling water pool and used to replenish the cooling pool of the production system.

4. The process according to claim 1, characterized in that In the above-mentioned S4, the material temperature is controlled at 50-80°C during the low-temperature concentration process.

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